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&&&&Section: &&&&&&&&SubSection: 2.6.6 Magnetic properties of materials
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2.6.6 Magnetic properties of materials
Many magnetic properties of materials
are expressed in terms of the magnetic field strength H, magnetic
flux density B and the magnetic polarization J. The
SI units of H and B are, respectively, ampere per
metre (A m&1) and tesla (T).
The relation between the quantities expressed in SI
&&&&&&&&&&&&&&B=
&0 is 4& &
10&7 H m&1, the magnetic constant
(permeability of free space). The absolute permeability, &( =
B/H) and the volume susceptibility &
(= J/&0H), are thus
related by the equation:
&&&&&&&&&&&&&
= &0(1 + &)
The mass susceptibility
& is equal to &/&, where
& is the density. The relative permeability
&r = &/&0 is the
permeability of the material relative to that of a vacuum and is the value
given in the tables.
In ferromagnetic materials as
H is increased steadily from zero the permeability changes and is
at first relatively small, its value being defined as the initial permeability,
then reaches a maximum value, and finally decreases towards
&0 as the polarization tends towards a limiting value
(B & &0H).
The flux density remaining when H is reduced to zero is the
remanent flux density and the negative H needed to reduce
B to zero is the coercive force. The remanent flux density and
coercive force for a cycle which proceeds to saturation are called the
remanence, Br, and the coercivity,
HcB. In an open magnetic circuit the variation of
J with H is usually measured and the coercivity is
then denoted by HcJ.
When a ferromagnetic material is taken
through a cycle of magnetization there is a loss of energy as heat due to the
combined effects of hysteresis, induced eddy currents and domain wall motion.
The hysteresis loss per unit volume,
Qh = H dB, has been shown empirically to vary
as B1.6max over a limited range of peak
flux density of up to about 1 T for high saturation materials, and 0.5 T for
low saturation materials. This relationship, known as the Steinmetz law, is
nevertheless only approximate. Some indication of the second loss, namely the
eddy current power loss, may be calculated from standard formulae once certain
relevant physical parameters are known. In their present forms, however, these
formulae are only approximate. The total power losses that will be dissipated
in laminar material when an alternating flux is developed in it has a direct
bearing on the efficiency that can be realized in equipment such as
transformers and electric motors and should therefore be known accurately.
Accordingly the power losses of representative forms of typical materials are
measured and some of these are given in Table (3) in terms of power loss per
unit mass.
Many magnetic properties of
ferromagnetic materials depend greatly on previous history, state of strain,
temperature, size, perfection and orientation of crystals, and the effect of
small traces of impurity may be enormous.
When heated, ferromagnetic materials
become paramagnetic at a temperature known as the (ferromagnetic) Curie
Ferrimagnetic materials (ferrites) have
all of the above characteristics of ferromagnetic materials. However, due to
their high resistivity, soft (low coercivity) ferrites are widely used in high
frequency applications, in which case the following parameters are also of
Power loss density&this is
another name for specific total power loss, but for ferrite materials the loss
is usually expressed per unit volume.
Loss factor&the performance
of ferrites at low field strengths is often indicated by the expression tan
& where & is the loss angle, i.e. the phase angle
between B and H. However,
information regarding power losses is usually given in the form of loss factors
normalized to unit permeability, &, since this facilitates the
calculation of loss coefficients of gapped ferrite cores. Hence the loss factor
where tan &h, tan
&e and tan &r are the loss
angles for the hysteresis, eddy current and residual losses respectively, all
of which are present to a greater or lesser extent and combine to give the
total loss, tan &.
IEC hysteresis coefficient
&B&in considering recommendations for standard
forms of loss expression, the International Electrotechnical Commission agreed
the following relationship for the hysteresis coefficient,
Temperature factor&the
permeability of a magnetic material may change for a variety of reasons, the
most obvious being the change of temperature. Over a limited temperature range
the relationship between the reversible change in magnetic permeability,
&D&, and the corresponding change in temperature,
&D&, is given by the temperature coefficient,
As with the loss factor, it is usual to normalize
the values to unit permeability which gives the loss factor:
loss factor =&
Disaccommodation factor&the
permeability of a magnetic material can also change with time after
magnetization. This phenomenon is often called disaccommodation. If the
permeabilities &1 and &2 correspond
to times t1 and t2 then the
disaccommodation is given by:
As with the loss and temperature
factors, the disaccommodation factor is normalized to unit permeability and is
disaccommodation factor =&
Apart from changes in their magnetic
permeability, some materials have other responses to changes in magnetic field
strength. All conducting materials exhibit the Hall effect, of which there are
two forms. In the transverse Hall effect a voltage is developed in a direction
at right angles to a current passing through the material when a magnetic field
is applied in a mutually perpendicular direction. The relationship between the
current flowing through the material Ix, the output
voltage, Vy, the thickness of the material,
tz, and the applied magnetic field strength,
Hz, is given by:
&&&&&&&&&&&&&Vy
(KH&Ix&&0&Hz)
where KH is the
transverse Hall coefficient of the material. It has been found that some
semiconducting materials have sufficiently high Hall coefficients to produce
convenient, small size and low cost magnetic sensors. Indium arsenide having a
Hall coefficient of 0.75 Vm/TA is a widely used material.
The same conditions that produce the
transverse Hall effect also give rise to a voltage in the direction of the
current and this is sometimes called the longitudinal Hall effect but more
usually magnetoresistance. Until recently only small changes in resistance have
been observed (up to 2% for the widely used
Ni80Fe20 material at room temperature) but the so-called
giant magnetoresistance (GMR) has been observed in multilayers of Fe/Cr
(50% change in resistance) and Co/Cu (120% change in resistance). However, strong magnetic field
strengths (& 800 kA/m) and a temperature of 4.2
K are required to observe GMR in a multilayer. In all cases the
magnetoresistance of a material is a complex function of the applied magnetic
field strength, temperature, material type and thickness.
Since the properties may vary
considerably from specimen to specimen due to chemical composition and state of
heat treatment, the values given are only to be regarded as typical of the
materials mentioned. A range of values is indicated by a dash.
Symbols used in tables:
magnetic flux density &&&Br &=
remanence &&&H &&= magnetic field
strength &&&HcB = induction
coercive force, coercivity &&&HcJ =
magnetization coervice force, coercivity &&&J
&&&= magnetic polarization
&0H)s = saturation
polarization &&&Qh&&=
hysteresis loss per unit volume per cycle
&&&&r &&= relative magnetic
permeability &&&&i &&=
initial relative magnetic permeability
Values are mass susceptibility per kilogram,
&, at 20&C.
Common elements
Hydrogen&&&.&&.&&.&&.&&.
&.&&.&&.&&.&&.
Germanium&&.&&.&&.&&.&&.
Oxygen.&&.&&.&&.&&.&&.&&.
+133.6&&&&
Copper&&&&&&.&&.&&.&&.&&.
Silicon&&&.&&.&&.&&.&&.&&.&&.
Helium&&&&.&&.&&.&&.&&.&&.
Silver&&&&&&.&&.&&.&&.&&.&&.
Arsenic&&&&.&&.&&.&&.&&.&&.
Neon&&&.&&.&&.&&.&&.&&.&&.
Gold&&&&&&&.&&.&&.&&.&&.&&.
Indium&&.&&.&&.&&.&&.&&.&&.
Argon&.&&.&&.&&.&&.&&.&&.
Platinum&&.&&.&&.&&.&&.&&.
Antimony&.&&.&&.&&.&&.&&.
Krypton&&&&.&&.&&.&&.&&.
Mercury&&.&&.&&.&&.&&.&&.
Tellurium&
.&&.&&.&&.&&.&&.
Xenon&&&&.&&.&&.&&.&&.&&.
Bismuth&&&.&&.&&.&&.&&.&&.
Gallium&&.&&.&&.&&.&&.&&.&&.
Nitrogen&&&.&&.&&.&&.&&.
Sulphur&&&.&&.&&.&&.&&.&&.
Phosphorus&.&&.&&.&&.&&.
Sodium&&&&&.&&.&&.&&.&&.
&&.&&.&&.&&.&&.&&.&&.
Potassium&.&&.&&.&&.&&.
Uranium&.&&.&&.&&.&&.&&.
Common compounds
Common materials
H2O&&&&&.&&.&&.&&.&&.&&.
NiSO47H2O&&&.&&.&&.
Araldite&&.&&.&&.&&.&&.&&.
NO&&&&&&.&&.&&.&&.&&.&&.
NiSO4K2SO47H2O
P.V.C&&&&.&&.&&.&&.&&.&&.
CO2&&&&&.&&.&&.&&.&&.&&.
CuSO45H2O&&.&&.&&.
Perspex&.&&.&&.&&.&&.&&.
NH3&&&&&.&&.&&.&&.&&.&&.
MnSO44H2O&.&&.&&.
Polyethylene&&&.&&.&&.
HCl&&&&&&.&&.&&.&&.&&.&&.
FeSO4(NH4)2&&&.&&.
H2SO4&&&&.&&.&&.&&.&&.
&&&SO46H2O&&&.&&.&&.
NaCl&&&&.&&.&&.&&.&&.&&.
NiCl2&&&.&&.&&.&&.&&.&&.
&&&&(anhydrous)&&.&&.
solution)&&.&&.
Approx.% composition (Balance iron)
&rfor H = 5
Aluminium silicon bronze
see BS 2872
and BS 2874
Aluminium nickel bronze
see ISO 428
High tensile brass CZ114
see BS 2872, BS 2874
&&&or HT1&
and ISO 426
Austenitic stainless
&&&AISI type:
&&&&&Ni 7.8, Cr
&&&Austenized
cold reduction
&&&55% cold
14.8&&&&&&
&&&&&Ni 9.0, Cr
&&&Austenized
&&&20% cold
&&&44% cold
&&&68% cold
&&&&&Ni 10.7, Cr
&&&Austenized
cold reduction
&&&32% cold
&&&65% cold
&&&&&Ni 11.7, Cr
&&&Austenized
cold reduction
cold reduction
&&&&&Ni 20.7, Cr
&&&Austenized
cold reduction
&&&&&Ni 13.4, Cr
&&&Austenized
&&&81% cold
&&&&&Ni 10.3, Cr 18.3, Ti
&&&Austenized
cold reduction
cold reduction
&&&&&Ni 10.7, Cr 18.4, Co
&&&Austenized
cold reduction
&&&40% cold
&&&60% cold
Material(approx. % composition , balance
H/(A m&1) =
Relative permeability &r
Curie point
Resistivity
Specific total
loss for J
apparent power for J
Ferromagnetic elements
&&&&Iron, high purity (single
&&&&&&&&crystals in
preferred direction)&&.&&.
iron&&&&&&.&&.&&.&&.&&.&&.&&.&&.&&.&&.&&.
&&&&Cast iron
(annealed)&&&&&.&&.&&.&&.&&.&&.&&.
&&&&Swedish iron
(annealed)&&&&&.&&.&&.&&.&&.
&&&&Nickel&&&&&&.&&.&&.&&.&&.&&.&&.&&.&&.&&.&&.&&.&&.&&.
&&&&Cobalt&&&&&&.&&.&&.&&.&&.&&.&&.&&.&&.&&.&&.&&.&&.&&.
Steels (solid)
&&&Carbon steel (annealed) 1% C&&.&&.&&.
&&&Constructional steels:
&&&&&&0.3%
&&&&&&0.4%
C, 3% Ni, 1.5%
Cr&&.&&.&&.&&.
&&&Mild steel, 0.1%
C&&&&.&&.&&.&&.&&.&&.&&.
Steels (sheet)&
&&&&Grain oriented silicon steels
&&&&preferred magnetic properties in
&&&&direction of rolling of the parent
&&&&(d.c. magnetization):
&&&&Unisil-H, 103-27-P5, (27MOH) 2.9%
1.00 (J = 1.7T)
1.38 (J = 1.7T)
&&&&Unisil,089-27-N5,(27M4)
&&&&&&&&&&&097-30-N5,
&&&&&&&&&&&111-35-N5,
&&&&Non-oriented silicon steels:
&&&&SURA &&300-35-A5, (CK-37)
&&&2.9% Si
&&&&&&&&&&&&&&&&&400-50-A5,
(CK-40) &&&2.4% Si
&&&&&&&&&&&&&&&&&800-65-A5,
(DK-70) &&&1.6% Si
&&&&Non-oriented, non-silicon steel:
&&&&Newcor
&&.&&.&&.&&.&&.&&.&&.
Amorphous iron&boron alloys
(metallic glass)
&&&&Metglas&D&&&2605
S-3&.&&.&&.&&.&&.&&.&&.
0.15 (J = 1.7T)
0.20 (J = 1.0T)
&&&&Metglas&&&&2605
SC&&.&&.&&.&&.&&.&&.&&.
Material(approx. % composition , balance
Flux density B/T for
H/(A m&1) =
Relative permeability &r
Curie point
Resistivity
Nickel iron alloys
&&Supermumetal&
&&Nilomag 771&
&&70&80% Ni with
&&Mumetal plus&
&&amounts of other
&&Mumetal&
&&elements
641&&&&&&&&&65% Ni +
small&&&&&&&&&&&&&&&&&&&&&&&&&&&amount
other&&&&&&&&&&&&&&&&&&&&&&&&&&&elements,
&&Nilomag 471&
Radiometal&
&&50% Ni + small
&&Radio metal
&&amounts of
&&other elements
&&Satmumetal&
&&HCR alloy&
+oriented structure
&&Radio metal 36&
&&Hyperm 36
constant permeability alloy
30% Ni, temperature
compensating alloy
Cobalt-iron
&&&Permendur 24 &24% Co
&&&Permendur 49 &49% Co
&&&Supermendur &&49% Co, 2% V
50&&&&&&&&&49% Co, 0.3% Ta
Other alloys
&&&Heusler
alloy&&&61% Cu, 26% Mn, 13%
&&&Isoperm&&&&&&&&&30% Ni, 11% Cu
constant permeability alloy
&&&Perminvar&&&&&&&40% Ni, 25% Co
constant permeability alloy
&&&Nickel copper&&70% Ni, 30% Cu
Initial relative permeability
Frequency range
Loss factor at maximum
Temperature factor
Flux density
Power loss density for B
= 0.2T,f = 16 kHz
IEC hysteresis coefficient
Disaccommodation factor
Curie point
Resistivity
Carbonyl iron powder cores
&&&&type 100
0.1&2&&&&&
&&&&type 500
&&&&type 900
&&&&type 901
Magnetic iron oxide powder
&&&&type 910
500(at 100 MHz)
Iron flake cores
&&&used for interference&&
suppression, relative&&&initial
permeability&&&falls rapidly
with&&&frequency
90 at 1 kHz
65 at 150 kHz
Ferrite cores
&&&(a) for radio, TV and
&&&&&&&&low power
&&&&&&&&nickel
&&&&&&&&&&&type
&&&&&&&&&&&type
&&&&&&&&&&&type
&&&&&&&1&10
&&&&&&&&&&&type
&&&&&&&5&40
&&&&&&&manganese zinc,
&&&&&&&&&&&type
&&&&&&&&&&&type
&&&&&&&&&&&type
&&&(b) perminvar, high
&&&&&&&&frequency low
&&&&&&&&uses
&&&&&&&&&&&
&&&&&&&&&&&
&&(c) manganese zinc for
&&&&&&&&high power uses
&&&&&&&&&&&
&&&&&&&&&&&
&&&(d) manganese zinc, high
&&&&&&&&stability, low
&&&&&&&&telecommunications
&&&&&&&&uses
&&&&&&&&&&&type
&&&&&&&&&&&type
&&&&&&&&&&&type
Approx. composition (balance
Remanence Br
Coercivity
Curie point
Maximum operating temperature
Resistivity
&&Ni 25, Al 13, Cu 4
&&Ni 19, Al 10, Co 12, Cu 6
Alcomax III
anisotropic
Ni 13.5, Al 8, Co 24, Cu 3
Alcomax III
semi-columnar
Alnico 5 DG
Alnico 5&7
Hycomax II &&&&&anisotropic
&&Ni 14.5, Al 7, Co 29,
&&&&&&&&&&&Cu
Hycomax III
anisotropic
Ni 14, Al 7.3, Co 34,
Cu 3, Ti 5.25
Alnico 9 columnar
Note: The isotropic and anisotropic alloys can also be prepared
by sintering, in which case the magnetic properties can be up to 20% less than
those for cast material.
Remanence Br
Coercivity
Curie point
Maximum operating temperature
Resistivity
Supermagloy, sintered
&&&&&&&pressed axially
&&&&&&&pressed isostatically
&&&&&&&anisotropic
&&&&&&&&&&&&Sm2Co17
&&&&&&&bonded
&&&&&&&&&&&&Sm
Co5 + binder
anisotropic
Magnequench, isotropic
&Nd Fe B + binder
&injection moulded,
&anisotropic
Approx. composition (balance iron)
Remanence Br
Coercivity
Curie point
Maximum operating temperature
Resistivity
&sintered isotropic
&sintered anisotropic
Ferroxdure 300
Ferroxdure 380
Ferroxdure 500
&bonded isotropic
&bonded anisotropic
A.E.Drake.
This site is hosted by the预购版本gta5线上被永封了怎么解除steeam绑定_百度知道
预购版本gta5线上被永封了怎么解除steeam绑定
我的是预购版本的，据说序列号和现在发售的版本不一样，能直接移除游戏然后重新买一个绑定新的sc帐号吗
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你先问问为什么永久封号了
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steam都把游戏装在哪里了
我在steam上买了两个游戏，其中有一个占空间还蛮大的，但是我选择安装的时候他并没有向我提示装在哪个盘 仅仅是告诉你游戏多大，你的硬盘还剩多少等等的信息，如此图。
我在电脑各个盘里都找不到游戏的文件夹在哪？请问我的游戏其实是装在哪个盘呢？？？？？...
我有更好的答案
STEAM上所有的游戏都放在STEAM文件夹内的steamapps文件夹下，在这个文件夹下有打包成GCF的游戏文件，有放置VALVE官方游戏的文件夹（具体文件夹名和你的帐号名一样），以及一个放置其他公司游戏的文件夹（文件夹名为common）。STEAM的游戏目前是无法更改安装路径的，必须要和STEAM装在同一个盘同一个目录下
采纳率：61%
在STEAM文件夹内的steamapps文件夹下
你把steam装在哪，游戏就装在哪。
具体应该在steam\steamapps\common
1条折叠回答
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苹果手机上部落冲突换了个号登、以前的就登不回去了，请问怎么才能登回去
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1.进入手机桌面，点击“设置”，进入设置页面，2.在设置页面下拉屏幕，找到“Game Center”单击进入，3.在“Game Center”页面，可以看到游戏账号，点击游戏账号即可切换。《部落冲突》是芬兰游戏公司Supercell oy所推出的策略类的游戏，该游戏以策略战争为主题，通过经营自己的村庄，玩家可逐渐强大兵力，进而与成千上万的玩家进行战斗，村庄到达一定等级后，还可与其他村庄结成部落，进行部落间的战斗。其内容兼具攻、守城及养成元素。这款游戏吸收了即时战略和塔防的游戏特点，建造房屋和炮塔、收集资源、训练士兵以及连网对战是这款游戏的主要元素。
去G am eca e ter把帐号换回以前的，再登进去就应该可以了。
本回答被网友采纳
gamecenter输入以前的apple
去Game center 把账号换回以前的，并在gc中进去游戏
去Game center 把账号换回以前的登入 再进游戏就好了
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